{"cvss":0.0,"datePublished":"2026-07-27T21:17:06.130","dateUpdated":"2026-11-03T18:15:39.353","description":"In the Linux kernel, the following vulnerability has been resolved:\n\nipv6: Fix null-ptr-deref in fib6_nh_mtu_change().\n\nfib6_nh_mtu_change() re-fetches idev via __in6_dev_get(arg->dev) and\ndereferences idev->cnf.mtu6 without a NULL check. addrconf_ifdown()\nclears dev->ip6_ptr with RCU_INIT_POINTER() after rt6_disable_ip() has\nreleased tb6_lock, so the RA-driven MTU walk can observe a NULL idev and\noops. The caller rt6_mtu_change_route() guards its own __in6_dev_get(),\nbut this re-fetch is unguarded; nexthop-backed routes survive\naddrconf_ifdown()'s flush, so the walk still reaches it after ip6_ptr is\nnulled.\n\nReturn 0 when idev is NULL, matching rt6_mtu_change_route() and the\nfib6_mtu() fix in commit 5ad509c1fdad (\"ipv6: Fix null-ptr-deref in\nfib6_mtu().\").\n\n  Oops: general protection fault, ... KASAN: null-ptr-deref in range\n        [0x00000000000002a8-0x00000000000002af]\n  RIP: 0010:fib6_nh_mtu_change+0x203/0x990\n   rt6_mtu_change_route+0x141/0x1d0\n   __fib6_clean_all+0xd0/0x160\n   rt6_mtu_change+0xb4/0x100\n   ndisc_router_discovery+0x24b5/0x2cb0\n   icmpv6_rcv+0x12e9/0x1710\n   ipv6_rcv+0x39b/0x410","id":"CVE-2026-64538","raw":{"affected":[{"affectedData":[{"defaultStatus":"unaffected","product":"Linux","programFiles":["net/ipv6/route.c"],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","vendor":"Linux","versions":[{"lessThan":"d08d019f2f43a6f9a71e81868bbc326b3afaf37b","status":"affected","version":"c0b220cf7d80eb8a36ae9f12cae6df4577a6814e","versionType":"git"},{"lessThan":"1451deca9896957159f0666520a792c1b861af4f","status":"affected","version":"c0b220cf7d80eb8a36ae9f12cae6df4577a6814e","versionType":"git"},{"lessThan":"b2c70dd3326809429b709a9c7e9220d29923051a","status":"affected","version":"c0b220cf7d80eb8a36ae9f12cae6df4577a6814e","versionType":"git"},{"lessThan":"302d57ed7872838b40e56a868fb4c7da7da606e9","status":"affected","version":"c0b220cf7d80eb8a36ae9f12cae6df4577a6814e","versionType":"git"},{"lessThan":"80600b5d0f3ecb9324120dc95b5e915130f516c5","status":"affected","version":"c0b220cf7d80eb8a36ae9f12cae6df4577a6814e","versionType":"git"},{"lessThan":"b0d0eb13a0441a8ebf4f227843deaf494f1e2c33","status":"affected","version":"c0b220cf7d80eb8a36ae9f12cae6df4577a6814e","versionType":"git"},{"lessThan":"6428634f7a0b7878144b4925c37856bef3224967","status":"affected","version":"c0b220cf7d80eb8a36ae9f12cae6df4577a6814e","versionType":"git"},{"lessThan":"46c3b8191aad3d032776bf3bebf03efdf5f4b905","status":"affected","version":"c0b220cf7d80eb8a36ae9f12cae6df4577a6814e","versionType":"git"}]},{"defaultStatus":"affected","product":"Linux","programFiles":["net/ipv6/route.c"],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","vendor":"Linux","versions":[{"status":"affected","version":"5.3"},{"lessThan":"5.3","status":"unaffected","version":"0","versionType":"semver"},{"lessThanOrEqual":"5.10.*","status":"unaffected","version":"5.10.261","versionType":"semver"},{"lessThanOrEqual":"5.15.*","status":"unaffected","version":"5.15.212","versionType":"semver"},{"lessThanOrEqual":"6.1.*","status":"unaffected","version":"6.1.178","versionType":"semver"},{"lessThanOrEqual":"6.6.*","status":"unaffected","version":"6.6.145","versionType":"semver"},{"lessThanOrEqual":"6.12.*","status":"unaffected","version":"6.12.97","versionType":"semver"},{"lessThanOrEqual":"6.18.*","status":"unaffected","version":"6.18.40","versionType":"semver"},{"lessThanOrEqual":"7.1.*","status":"unaffected","version":"7.1.5","versionType":"semver"},{"lessThanOrEqual":"*","status":"unaffected","version":"7.2","versionType":"original_commit_for_fix"}]}],"source":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"affectedData":[{"defaultStatus":"unknown","product":"SIMATIC S7-1500 CPU 1518-4 PN/DP MFP","vendor":"Siemens","versions":[{"lessThan":"*","status":"affected","version":"V3.1.6","versionType":"custom"}]},{"defaultStatus":"unknown","product":"SIMATIC S7-1500 CPU 1518-4 PN/DP MFP","vendor":"Siemens","versions":[{"lessThan":"*","status":"affected","version":"V3.1.7","versionType":"custom"}]},{"defaultStatus":"unknown","product":"SIMATIC S7-1500 CPU 1518-4 PN/DP MFP","vendor":"Siemens","versions":[{"lessThan":"*","status":"affected","version":"V3.1.6","versionType":"custom"}]},{"defaultStatus":"unknown","product":"SIMATIC S7-1500 CPU 1518-4 PN/DP MFP","vendor":"Siemens","versions":[{"lessThan":"*","status":"affected","version":"V3.1.7","versionType":"custom"}]},{"defaultStatus":"unknown","product":"SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP","vendor":"Siemens","versions":[{"lessThan":"*","status":"affected","version":"V3.1.6","versionType":"custom"}]},{"defaultStatus":"unknown","product":"SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP","vendor":"Siemens","versions":[{"lessThan":"*","status":"affected","version":"V3.1.7","versionType":"custom"}]},{"defaultStatus":"unknown","product":"SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP","vendor":"Siemens","versions":[{"lessThan":"*","status":"affected","version":"V3.1.6","versionType":"custom"}]},{"defaultStatus":"unknown","product":"SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP","vendor":"Siemens","versions":[{"lessThan":"*","status":"affected","version":"V3.1.7","versionType":"custom"}]},{"defaultStatus":"unknown","product":"SIPLUS S7-1500 CPU 1518-4 PN/DP MFP","vendor":"Siemens","versions":[{"lessThan":"*","status":"affected","version":"V3.1.6","versionType":"custom"}]},{"defaultStatus":"unknown","product":"SIPLUS S7-1500 CPU 1518-4 PN/DP MFP","vendor":"Siemens","versions":[{"lessThan":"*","status":"affected","version":"V3.1.7","versionType":"custom"}]}],"source":"0b142b55-0307-4c5a-b3c9-f314f3fb7c5e"}],"cveTags":[],"descriptions":[{"lang":"en","value":"In the Linux kernel, the following vulnerability has been resolved:\n\nipv6: Fix null-ptr-deref in fib6_nh_mtu_change().\n\nfib6_nh_mtu_change() re-fetches idev via __in6_dev_get(arg->dev) and\ndereferences idev->cnf.mtu6 without a NULL check. addrconf_ifdown()\nclears dev->ip6_ptr with RCU_INIT_POINTER() after rt6_disable_ip() has\nreleased tb6_lock, so the RA-driven MTU walk can observe a NULL idev and\noops. The caller rt6_mtu_change_route() guards its own __in6_dev_get(),\nbut this re-fetch is unguarded; nexthop-backed routes survive\naddrconf_ifdown()'s flush, so the walk still reaches it after ip6_ptr is\nnulled.\n\nReturn 0 when idev is NULL, matching rt6_mtu_change_route() and the\nfib6_mtu() fix in commit 5ad509c1fdad (\"ipv6: Fix null-ptr-deref in\nfib6_mtu().\").\n\n  Oops: general protection fault, ... KASAN: null-ptr-deref in range\n        [0x00000000000002a8-0x00000000000002af]\n  RIP: 0010:fib6_nh_mtu_change+0x203/0x990\n   rt6_mtu_change_route+0x141/0x1d0\n   __fib6_clean_all+0xd0/0x160\n   rt6_mtu_change+0xb4/0x100\n   ndisc_router_discovery+0x24b5/0x2cb0\n   icmpv6_rcv+0x12e9/0x1710\n   ipv6_rcv+0x39b/0x410"}],"id":"CVE-2026-64538","lastModified":"2026-11-03T18:15:39.353","metrics":{},"published":"2026-07-27T21:17:06.130","references":[{"source":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","url":"https://git.kernel.org/stable/c/1451deca9896957159f0666520a792c1b861af4f"},{"source":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","url":"https://git.kernel.org/stable/c/302d57ed7872838b40e56a868fb4c7da7da606e9"},{"source":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","url":"https://git.kernel.org/stable/c/46c3b8191aad3d032776bf3bebf03efdf5f4b905"},{"source":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","url":"https://git.kernel.org/stable/c/6428634f7a0b7878144b4925c37856bef3224967"},{"source":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","url":"https://git.kernel.org/stable/c/80600b5d0f3ecb9324120dc95b5e915130f516c5"},{"source":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","url":"https://git.kernel.org/stable/c/b0d0eb13a0441a8ebf4f227843deaf494f1e2c33"},{"source":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","url":"https://git.kernel.org/stable/c/b2c70dd3326809429b709a9c7e9220d29923051a"},{"source":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","url":"https://git.kernel.org/stable/c/d08d019f2f43a6f9a71e81868bbc326b3afaf37b"},{"source":"0b142b55-0307-4c5a-b3c9-f314f3fb7c5e","url":"https://cert-portal.siemens.com/productcert/html/ssa-019113.html"},{"source":"0b142b55-0307-4c5a-b3c9-f314f3fb7c5e","url":"https://cert-portal.siemens.com/productcert/html/ssa-457936.html"}],"sourceIdentifier":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","vulnStatus":"Awaiting Analysis"},"severity":"UNKNOWN","source":"nvd","title":"In the Linux kernel, the following vulnerability has been resolved:\n\nipv6: Fix null-ptr-deref in fib6_nh_mtu_change()..."}